Silver nanoparticles have a multitude of valuable applications in the rapidly emerging fields of nanoscience and nanotechnology. Powerful surface plasmon absorption of nanoparticulate silver makes them particularly useful in applications such as biosensors, for example. Silver nanoparticles are a photo-fluorescence marker, which makes them useful for a number of medical and similar applications. They are environmentally and biologically benign. Other exemplary silver nanoparticle applications include smart windows, rewritable electronic paper, electronic panel displays, memory components, and others.
Traditional methods for the production of silver nanoparticles require use of potentially harmful chemicals such as hydrazine, sodium borohydride and dimethyl formamide (“DMF”). These chemicals pose handling, storage, and transportation risks that add substantial cost and difficulty to the production of silver nanoparticles. A highly trained production workforce is required, along with costly production facilities outfitted for use with these potentially harmful chemicals.
These harmful chemicals also make it impractical, if not impossible, to produce silver nanoparticles in-vivo. This limitation results in silver nanoparticles having to be prepared beforehand, sanitized, and then introduced to a body for many medical applications. These extra steps add cost and effort. Also, the complexity of handling silver nanoparticles for these applications further limits their use in such applications.
Another disadvantage of known methods for producing silver nanoparticles relates to the time and heat required for their production. Known methods of production utilize generally slow kinetics, with the result that reactions take a long period of time. The length of time required may be shortened by some amount by applying heat, but this adds energy costs, equipment needs, and otherwise complicates the process. Known methods generally require reaction for 20 or more hours at elevated temperatures of 60°-80 C., for example. The relatively slow kinetics of known reactions also results in an undesirably large particle size distribution and relatively low conversion. The multiple stages of production, long reaction times at elevated temperatures, relatively low conversion, and high particle size distribution of known methods make them costly and cumbersome, particularly when practiced on a commercial scale.
These and other problems with presently known methods for making silver nanoparticles are exacerbated through the relatively unstable nature of the nanoparticles. Using presently known methods, the silver nanoparticles produced have only a short shelf life since they tend to quickly agglomerate.
As a result of these and other problems, unresolved needs remain in the art.